The present invention relates to a method of forming an insulating layer on a multi-layer printed circuit board and a printed circuit board having such an insulating layer.
In a method of manufacturing the multi-layer printed circuit board, a silk screen printing is performed on a circuit pattern with an insulating ink, and a conductive ink, for example, a carbon ink, a silver paste ink or the like is provided on the insulating ink by the silk screen printing method, thereby forming a jumper wire.
In this case, it is important to perform provides an insulation between the circuit pattern and the jumper wire which are formed on the insulating base material plate. In the case of a circuit pattern having density and complicated shape, however, it is difficult using screen printing to introduce the insulating ink between the circuit patterns and a problem formation of pin-hole arises, so that provision of an insulation between the conductive layers can not be completely performed. Therefore, a problem of the reliability in formation of film arises.